Diastolically phased pulsed intra-arterial infusions have been shown to be an effective means to produce concentration uniformity in downstream branches of a model of the cerebral circulation. The technique is being evaluated in the cerebral circulation of fully anesthetized Rhesus monkeys by the infusion of radio-isotope labelled iodoantipyrine into the internal carotid artery. The resulting tissue concentration is determined by quantification of autoradiographs. Initial results show high uniformity of tissue concentration, indicating that the deleterious effects of infusate streaming can be alleviated.